1. Field of the Invention
The present invention relates to a circuit module and a composite circuit module, and more specifically, relates to a circuit module and a composite circuit module, which include surface acoustic wave filters including piezoelectric elements.
2. Description of the Related Art
As a circuit module of the related art, an electronic component device described in, for example, Japanese Unexamined Patent Application Publication No. 2002-299996 has been known. FIG. 9 is the cross-sectional structural view of an electronic component device 500 described in Japanese Unexamined Patent Application Publication No. 2002-299996.
The electronic component device 500 includes a SAW device 502 and a base substance 504. The SAW device 502 includes a piezoelectric single crystal substrate 506 and a comb-shaped electrode 508. The comb-shaped electrode 508 is provided on the piezoelectric single crystal substrate 506. The SAW device 502 is mounted on the base substance 504 through bumps so that the comb-shaped electrode 508 faces the base substance 504. The electronic component device 500 configured in such a way as described above is mounted in, for example, a mother substrate and used.
Incidentally, when the electronic component device 500 is heated or cooled in a reflow process or the like, there is a possibility that a connection to or within the device may be damaged. In more detail, in the electronic component device 500, the piezoelectric single crystal substrate 506 is manufactured using, for example, lithium tantalate. In addition, the base substance 504 is manufactured using, for example, a ceramic such as aluminum oxide. In addition, the mother substrate is manufactured using, for example, a glass epoxy resin. The lithium tantalate, the aluminum oxide, and the glass epoxy resin are different from one another in material properties such as a coefficient of linear expansion and a Young's modulus. Therefore, when the electronic component device 500 has been heated or cooled in the reflow process or the like, different deformations may occur in the SAW device 502, the base substance 504, and the mother substrate. As a result, there is a possibility that a connection to or within the electronic component device 500 may be damaged. Using a computer simulation, the present inventor ascertained that a connection between the SAW device 502 and base substance 504 has a special propensity to be damaged.